Transformers are commonly used in welding type power supplies. Welding type power supply, as used herein, is a power supply that provides a welding type output. Welding type output, as used herein, is an output suitable for welding, plasma cutting, or induction heating. Welding type power supplies have a wide variety of topologies. For example, they can include a preregulator to provide a bus, and have an output converter that converts the bus into a desired current and voltage. Examples of preregulators include boosts, bucks, rectifiers, etc. Examples of output converters, include inverters, boosts, bucks, choppers, etc. Welding type power supplies can have additional, intermediate stages, and can receive utility power as input power, or include a generator.
Many welding type power supplies include an auxiliary power output. This is often provided at 120 volts (or other utility voltages power), and can be derived by transforming input power, or derived from a bus by a converter (such as inverter). Auxiliary power derived by inverting the bus is also usually transformed (to provide the desired 120V ac). Thus, when auxiliary power is provided it is common to have an auxiliary power transformer. Auxiliary power, as used herein, includes power provided other than on the main power output of a welding type power supply.
Many welding type power supplies include a weld power transformer that handles the primary welding type output of the power supply. Weld power transformers can become overheated and are typically cooled by a fan (or fans). Some prior art welding type power supplies turn the fan(s) on and off as needed, in response to the temperature of the welding transformer.
The auxiliary power transformer is often cooled by the same fan as the weld transformer. However, the prior art does not use the temperature of the auxiliary transformer to determine when the fan should be turned on and off. Thus, cooling is only provided when the weld transformer becomes hot. Accordingly, a welding-type power supply that has an auxiliary power transformer that is cooled by a fan controlled in response to the auxiliary power transformer temperature is desired.